Axiom Audio made many
reviewers, including me, stand up and take notice when they released two bone-rattling
subwoofers, the EP600 and the EP500. These subs feature Axioms custom DSP algorithm,
which offers unprecedented (in my experience) control over the subs amplifier and
driver to produce clean, undistorted sound. These models are relatively big, especially
the EP600, which resembles a floorstanding speaker. However, many people who dont
have room for such a huge subwoofer still want deep bass. For them, Axiom has introduced
the EP400, which packs a lot of technology into its small enclosure and costs only $1100.

Inside the EP400

Small is too big a word to describe the EP400. Try tiny:
13.75"H x 10.5"W x 16.8"D. It would be easy to dismiss the EP400 as a
run-of-the-mill sub -- until you looked around back. There youd see a couple of
clues that indicate that its a serious piece of high-end gear: the presence of a
balanced input and output. Theres also its hefty weight of 48.5 pounds. I have a
bevy of small subwoofers in my house, and none approaches the EP400s density.

Responsible for much of
this weight are the 8" aluminum-cone woofer and the amplifier-and-control-panel
assembly. The driver has a large-diameter voice-coil for vise-like control over the
movement of the cone. The amplifier is Axioms proprietary 500W module, which
features an analog power supply coupled to a high-efficiency digital switching amplifier.
The control panel has a switch for switching the phase from 0 to 180 degrees, dials for
setting the volume and crossover frequency (from 40 to 150Hz), and a room-trim control for
boosting, cutting, or flattening the EP400s output.

When unpacking the EP400, I noticed its lack of a port or a
passive radiator. I even flipped it over to make sure. This made no sense to me -- the
EP500 and EP600 have ports. A port would allow higher output from a smaller box; surely
the tiny EP400 needed the help? An e-mail from Amie Colquhoun of Axiom provided the
answer: digital signal processing. A DSP algorithm is programmed in the EP400 to allow a
lot of movement by the woofer with little distortion. Given the EP400s design
criteria of small size and deep bass response, Axiom found there was no room for a port,
and that the DSP circuit meant that none was needed. Cant argue with that.

Performance

I initially set up the Axiom EP400 in my main listening
room, near the front left corner, about 9 from my listening seat. The room-trim
control was set to Flat. I used the EP400 with Axioms M3 v2 bookshelf speakers,
the Mirage Nanosat Prestige, and the PSB Alpha Mini systems. With the EP400s
crossover control set to Bypass, I varied my receivers crossover setting from 80 to
120Hz to accommodate each systems bass response.

The EP400 proved to be a great performer with music. With
acoustic bass, it had texture and finesse, without the constant drone of one-note bass I
often hear from lesser subs. A good example of this was Holy Coles Temptation
[CD, Alert Z281026]. Bassist David Pilchs deft playing in "Jersey Girl"
came alive through the EP400, each note distinct enough that I could picture his fingers
at work.

As good as the EP400 was with music, I felt a little
underwhelmed when I used it with movies. I watched the Blu-ray edition of the recent
version of Casino Royale, whose uncompressed PCM 5.1 soundtrack contains lots of
deep-bass effects. Near the end is a scene in which a building in Venice is destroyed.
Although the EP400 put out decent sound levels, I wasnt blown out of my seat as
Id expected to be, especially after having recently watched this scene with
Axioms much larger EP500 sub in the system. Switching the trim control from Flat to
Full made a difference -- I heard greater output, though still not to the level of the
EP500.

This was entirely understandable, but still, something
seemed amiss. Using test tones, I confirmed that the EP400s cone moved with 20Hz
tones, although I heard nothing even with the volume control at max. To make sure nothing
was wrong with my sample, I spoke with Ian Colquhoun, head honcho of Axiom. He suspected
that my 20 by 14 room was probably a bit big for the EP400, which was designed
more for smaller spaces such as a bedroom or den. He offered to send another EP400 to see
if it performed any differently from the first, and if it didnt, that I then hook up
both subs to my system. I readily agreed.

When a subwoofer manufacturer suggests buying more units to
get higher bass output, youre probably right to be skeptical. Still, a second sub
will increase the overall low-bass output by 3dB, as well as distribute low-frequency
soundwaves more evenly throughout the room. The second EP400 did that, and completely
changed my opinion of the sub.

One Blu-ray disc with great sound is Ghost Rider,
whose soundtrack includes both uncompressed linear PCM and Dolby TrueHD tracks. With both,
there is much use of the LFE channel, such as the chop chop chop sound of a
motorbike throughout. The dual EP400s not only did justice to these sounds, they made it
feel as if a Harley was in my listening room. The explosions in Ghost Rider were
loud enough to shake my walls, something I hadnt experienced with only a single
EP400. The tightness of the bass was intact; Im sure the EP400s sealed box
helped in this regard. With two subs instead of one, I heard less of a volume difference
as I walked around the room. The output approached what I remember getting from an Axiom
EP500, not just at one seat but consistently throughout my listening room.

Comparison

I had on hand a Paradigm UltraCube 10 subwoofer, which
provided a good comparison with the Axiom EP400. The UltraCube 10 retails for $799, and
has a downward-firing 10" woofer, and two passive radiators on the sides. To the
naked eye, the Axioms build quality looks a few notches higher than the
Paradigms. The EP400s control panel exudes class, and adjusting the knobs
simply feels better. The Axioms connection options are far more comprehensive, too.
The UltraCube 10 has only a single LFE input, and its crossover cant be bypassed.
The EP400 has inputs and outputs, which are handy for daisy-chaining multiple subwoofers.

The UltraCube 10 held its own against the EP400. The Axiom
could play lower in frequency than the Paradigm, but the latter had higher output into my
room. This was noticeable when watching the DVD of Superman Returns, a sonic treat
that gave both subs a thorough workout. As Lex Luthor unleashes an electromagnetic pulse,
the LFE channel shook my floor and walls through the UltraCube 10, something a single
EP400 couldnt match. With music, however, the EP400 performed with better pitch
definition than the UltraCube 10, which made listening to SuperBass 2 from Ray
Brown, John Clayton, and Christian McBride [SACD, Telarc SACD-63483], a more enjoyable
experience.

Conclusion

If you have a high-end home theater in a room as small as
the typical den and youre after tight bass, I recommend the Axiom EP400. However, if
your room is, like mine, a larger one, then spending a bit more ($130) for the
EP500 v2 might result in a better fit. However, when giving the Axiom EP400 the full
shakedown, I learned that two EP400s is a possibly better alternative -- it resulted in
more evenly distributed low bass throughout my room. If your room is bigger but more
suited to two smaller EP400s than a single big sub, give it a shot -- you may find that it
works like a charm.